Thermal interface material having different thicknesses in packages

Abstract

A package includes a package component, a device die over and bonded to the package component, a metal cap having a top portion over the device die, and a thermal interface material between and contacting the device die and the metal cap. The thermal interface material includes a first portion directly over an inner portion of the device die, and a second portion extending directly over a corner region of the device die. The first portion has a first thickness. The second portion has a second thickness greater than the first thickness.

What is claimed is: 
     
         1 . A structure comprising:
 a first package component;   a first device die and a second device die over and joined to the first package component;   a metal cap comprising a top portion over the first device die and the second device die; and   a thermal interface material over the metal cap and underlying the top portion of the metal cap, wherein the thermal interface material comprises:
 a first portion directly over a portion of the first device die, wherein the first portion has a first thickness; and 
 a second portion, wherein the second portion overlaps a space between the first device die and the second device die, and wherein the second portion has a second thickness greater than the first thickness. 
   
     
     
         2 . The structure of  claim 1 , wherein the second portion of the thermal interface material comprises a part in the metal cap, and the part is in contact with sidewalls of the metal cap. 
     
     
         3 . The structure of  claim 2 , wherein in a cross-section view of the structure, the part of the second portion of the thermal interface material comprises straight edges. 
     
     
         4 . The structure of  claim 2 , wherein the part of the second portion of the thermal interface material comprises:
 a first edge vertically aligned to a second edge of the first device die; and   a third edge vertically aligned to a fourth edge of the second device die.   
     
     
         5 . The structure of  claim 1  further comprising an encapsulant encircling both of the first device die and the second device die. 
     
     
         6 . The structure of  claim 5 , wherein the second portion of the thermal interface material further overlaps a portion of the encapsulant. 
     
     
         7 . The structure of  claim 1 , wherein the metal cap further comprises a ring-shaped skirt portion under and joined to the top portion, wherein the top portion of the metal cap comprises a ring portion on an inner side of the ring-shaped skirt portion, wherein a third portion of the thermal interface material overlapped by the ring portion has a third thickness greater than the first thickness. 
     
     
         8 . The structure of  claim 7 , wherein the third portion of the thermal interface material comprises:
 a first part overlapping the first device die; and   a second part laterally beyond the first device die.   
     
     
         9 . The structure of  claim 7 , wherein the ring-shaped skirt portion forms a ring in a top view of the structure. 
     
     
         10 . The structure of  claim 1 , wherein the first portion of the thermal interface material contacts the first device die to form an interface, and at least a portion of the interface is parallel to or in a same plane as a major top surface of the first device die. 
     
     
         11 . The structure of  claim 1 , wherein the metal cap further comprises a ring-shaped skirt portion under and joined to the top portion, wherein the top portion of the metal cap comprises four corner portions on an inner side of the ring-shaped skirt portion, wherein third portions of the thermal interface material overlapped by the four corner portions have a third thickness greater than the first thickness. 
     
     
         12 . A structure comprising:
 a stack comprising:
 an interposer; 
 a first device die and a second device die over and connecting to the interposer; 
 a package substrate underlying and connecting to the interposer; and 
 an encapsulant comprising a middle portion between the first device die and the second device die; 
   a metal cap comprising a top portion, wherein the top portion overlaps the first device die and the second device die; and   a thermal interface material comprising:
 a planar portion having a substantially uniform thickness; and 
 a protruding portion protruding into the metal cap and overlapping the middle portion of the encapsulant. 
   
     
     
         13 . The structure of  claim 12 , wherein the metal cap further comprises a skirt portion underlying and connecting to the top portion. 
     
     
         14 . The structure of  claim 12 , wherein the planar portion comprises two portions overlapping the first device die and the second device die, and wherein the protruding portion protrudes higher than top surfaces of the two portions. 
     
     
         15 . The structure of  claim 12 , wherein in a top view of the structure, the protruding portion has a strip shape. 
     
     
         16 . The structure of  claim 12 , wherein edges of the protruding portion are vertically aligned to edges of the first device die and the second device die. 
     
     
         17 . A structure comprising:
 a package substrate;   an interposer over and connecting to the package substrate;   a first device die and a second device die over and connecting to the interposer;   a metal cap comprising:
 a top portion comprising:
 a first portion and a second portion directly over the first device die and the second device die, respectively, wherein the first portion and the second portion have a first thickness; and 
 a third portion overlapping a space between the first device die and the second device die, wherein the third portion has a second thickness smaller than the first thickness; and 
 
 a skirt portion underlying and joined to the top portion; and 
   a thermal interface material underlying and joined to the top portion.   
     
     
         18 . The structure of  claim 17 , wherein the thermal interface material contacts bottom surfaces of the first portion, the second portion, and the third portion. 
     
     
         19 . The structure of  claim 17  further comprising a molding compound encircling the first device die, wherein the thermal interface material is over and contacting both of the first device die and the molding compound. 
     
     
         20 . The structure of  claim 19 , wherein the molding compound comprises a middle portion between and contacting the first device die and the second device die, wherein the third portion overlaps the middle portion of the molding compound.